The Aim of the paper is to let the reader look at dependability through the eyes of a designer who is to develop an entity with specified dependability requirements. The result of such work is not yet dependability as a property, but the ability proper to a structure, without which the required dependability cannot manifest itself. Designing highly dependable entities requires the use of formalized practices with specific operating procedures, that, on the one hand, do not contradict the provisions of the dependability theory, while, on the other hand, are to be useful, clear and easy-to-understand by any designer in order to ensure the required dependability. Methods. The paper examines the primary approaches that allow a designer, without violating the existing notions and terminology of dependability, solving problems of technical object dependability in the course of design and development based on engineering disciplines and design methods intended to ensure the dependability of products, starting with the very early life cycle stages. If such approaches to dependability research are employed, preventing failures only requires the application of the principles of physicality (causal connections) and physical necessity (consistency with the laws of nature) of the causes of failures. Results. The paper sets forth simple mathematical models that helped create a generalized parametric model of complex technical systems operation. Based on the cited models, it can be concluded that dependability calculation in terms of the known dependability indicators of components and elements can be replaced with dependability estimation in terms of the probability of performance by the components and elements of the required functions. This conclusion not only does not contradict the provisions of the dependability theory, but makes dependability an effective tool helping the designer ensure the specified dependability. The generalized parametric model of operation is solved using the method of design and process dependability analysis developed for the purpose of analyzing and assessing design solutions as part of high-dependability item design. Conclusion. The concepts, approaches, models and methods suggested in the paper allow the designer to take dependability as operability expanded in time. Such dependability is always specific and takes into consideration all the distinctive features of an entity. In this case, the process of design and assurance of dependability becomes an integral part of the entity creation activities regardless of uniqueness, series production, availability of dependability indicators of components and elements. But most importantly, such approach to dependability, on the one hand, does not contradict the foundations of the modern dependability theory, and, on the other hand, relieves the designer of the impression that dependability is something foreign, not associated with the real design.